Published April 29, 1964: A workman fastens a vial of anti-Dutch elm disease serum to a tree in Washington Park. The large tree is one of about 100 on city property to be treated in Dubuque this week on an experimental basis. The containers hold serum that is deadly to elm bark beetles, carriers of the fungus that causes Dutch elm disease. The serum flows through hollow metal tubes into the tree’s vein system and it is carried to the branches. The workman, Robert Hatfield, wears an apron, gloves and mask to protect himself from the highly toxic serum. It has been used in Milwaukee and found to be 99.6 percent effective in combating the tree malady. J.J. Mauget Co., Centerville, IA, is treating the trees on a contract with the Dubuque Park Board.